ONE-EIGHTH STAGE 2026
Aburi Girl's SHS: 38 points
St. Joseph's Seminary SHS: 20 points
Fafraha Community SHS: 12 points
St. John's Grammar School: 40 points
Mpraeso SHS: 23 points
Tema Secondary School: 13 points
St. Augustine's College
Anlo SHS
Kumasi High School
ROUND 2 - SPEED RACE
QUESTION
Determine the number of sigma ($\sigma$) and pi ($\pi$) bonds present in one molecule of propyne.
ANSWER: 6 sigma ($\sigma$) bonds and 2 pi ($\pi$) bonds
SOLUTION:
Molecular formula of propyne: $C_3H_4$ (3 C + 4 H = 7 total atoms)
$\text{sigma bonds} = \text{total atoms} - 1$
$\text{sigma bonds} = 7-1$
$\text{sigma bonds} = 6$
Propyne contains one $C\equiv C$ triple bond (1 sigma + 2 pi)
$\text{pi bonds} = 2$
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PRACTICE QUESTIONS
1. QUESTION: Determine the number of sigma ($\sigma$) and pi ($\pi$) bonds present in one molecule of propene.
ANSWER: sigma bonds: 8; pi bonds: 1
SOLUTION:
Molecular formula of propene: $C_3H_6$
$\text{total atoms} = 9$
$\text{sigma bonds} = \text{total atoms} - 1$
$\text{sigma bonds} = 9 - 1$
$\text{sigma bonds} = 8$
Propene has one $C=C$ double bond (1 sigma + 1 pi)
Pi bonds: 1
2. QUESTION: Determine the number of sigma ($\sigma$) and pi ($\pi$) bonds present in one molecule of ethanal.
ANSWER: sigma bonds: 6; pi bonds: 1
SOLUTION:
Molecular formula of ethanal: $C_2H_4O$
$\text{total atoms} = 7$
$\text{sigma bonds} = \text{total atoms} - 1$
$\text{sigma bonds} = 7 - 1$
$\text{sigma bonds} = 6$
Ethanal has one $C=O$ double bond (1 sigma + 1 pi)
Pi bonds: 1
3. QUESTION: Determine the number of sigma ($\sigma$) and pi ($\pi$) bonds present in one molecule of propenal.
ANSWER: sigma bonds: 7; pi bonds: 2
SOLUTION:
Molecular formula of propenal: $C_3H_4O$
$\text{total atoms} = 8$
$\text{sigma bonds} = \text{total atoms} - 1$
$\text{sigma bonds} = 8 - 1$
$\text{sigma bonds} = 7$
Propenal has one $C=C$ and one $C=O$ double bond (1 pi each)
Pi bonds: 2
4. QUESTION: Determine the number of sigma ($\sigma$) and pi ($\pi$) bonds present in one molecule of ethene.
ANSWER: sigma bonds: 5; pi bonds: 1
SOLUTION:
Molecular formula of ethene: $C_2H_4$
$\text{total atoms} = 6$
$\text{sigma bonds} = \text{total atoms} - 1$
$\text{sigma bonds} = 6 - 1$
$\text{sigma bonds} = 5$
Ethene has one $C=C$ double bond (1 sigma + 1 pi)
Pi bonds: 1
5. QUESTION: Determine the number of sigma ($\sigma$) and pi ($\pi$) bonds present in one molecule of propyne.
ANSWER: sigma bonds: 6; pi bonds: 2
SOLUTION:
Molecular formula of propyne: $C_3H_4$
$\text{total atoms} = 7$
$\text{sigma bonds} = \text{total atoms} - 1$
$\text{sigma bonds} = 7 - 1$
$\text{sigma bonds} = 6$
Propyne has one $C\equiv C$ triple bond (1 sigma + 2 pi)
Pi bonds: 2
6. QUESTION: Determine the number of sigma ($\sigma$) and pi ($\pi$) bonds present in one molecule of buta-1,3-diene.
ANSWER: sigma bonds: 9; pi bonds: 2
SOLUTION:
Molecular formula of buta-1,3-diene: $C_4H_6$
$\text{total atoms} = 10$
$\text{sigma bonds} = \text{total atoms} - 1$
$\text{sigma bonds} = 10 - 1$
$\text{sigma bonds} = 9$
Buta-1,3-diene has two $C=C$ double bonds (1 pi each)
Pi bonds: 2